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Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 

* 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  ntp: Clamp PLL update interval
This commit is contained in:
Linus Torvalds 2010-10-21 14:08:08 -07:00
parent b61f6a57f1 8af3c153ba
commit 62bea97f54
1 changed files with 11 additions and 3 deletions
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14
kernel/time/ntp.c
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@ -149,10 +149,18 @@ static void ntp_update_offset(long offset)
time_reftime = get_seconds();
offset64 = offset;
freq_adj = (offset64 * secs) <<
(NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
freq_adj = ntp_update_offset_fll(offset64, secs);
freq_adj += ntp_update_offset_fll(offset64, secs);
/*
* Clamp update interval to reduce PLL gain with low
* sampling rate (e.g. intermittent network connection)
* to avoid instability.
*/
if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
secs = 1 << (SHIFT_PLL + 1 + time_constant);
freq_adj += (offset64 * secs) <<
(NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);